You are free to propose any project idea that meets the requirements outlined in the assignment description. However, many of the very best class projects are motivated by a "real world" problem. These projects attempt to solve an information problem faced by real users and use real data to prototype their visual analytics solution.
I encourage you to find your own "real world" problem. Talk to people that you know around UNC. Talk to organizations that you belong to or support. Chances are they have a dataset or two sitting around and a wish to learn or share insights about the data if they only had the time or tools to do it. That makes an ideal setting for a project. If you are stuck, I might be able to point you to a potential "client" who has a need from an existing project.
Meanwhile, I often have a couple of my own problems that can be used for a class project. These usually require some substantial programming skills, beyond the minimal skillset required for the individual homeworks. They may also allow a smaller, more focused team. If you are interested in exploring these possibilities, contact me to set up an appointment for us to discuss your options.